An anxiolytic drug (minor tranquilizer) is a therapeutic agent which is effective in treating anxiety and which can eliminate anxiety or psychentonia in a dose that will not induce excessive sedation. A typical therapeutic agent which is presently used as an anxiolytic drug is a benzodiazepine-type anxiolytic.
Heretofore, (1) bromacil (see Japanese Patent Laid-Open Publication No. 42624/1982), and (2) N.sup.3 -substituted (e.g., benzyl-substituted) uridine derivatives (see Japanese Patent Laid-Open Publication No. 207218/1987) have been known as uracil derivatives having anxiolytic activity or being expected to have the same.
We previously found that 1-amino-5-halogenouracil has sedative effects on central nervous system, and filed therefore an application for a patent (PCT/JP89/00708). As a 1-amino-5-halogenouracil, 1-amino-5-fluorouracil is so far known. However, it has not yet been reported that the compound has anxiolytic activity (see Sci. Pharm., 52, 46 (1984); and Japanese Patent Laid-Open Publication No. 93281/1987).
Benzodiazepine-type anxiolytic drugs which are now widely used as anxiolytic drugs, typically diazepam, give rise to various side effects (e.g-, muscle relaxation, sedation, and elicitation of amnesia). The use of the anxiolytic drugs of this type therefore brings about clinical problems. Since the above side effects are common to compounds having a benzodiazepine skeleton, there exists a demand for finding out a compound which has a skeleton other than the benzodiazepine and which can be used as an anxiolytic drug.
Further, among the above-described uracil derivatives having anxiolytic activity, the bromacil referenced as (1) exhibits low anxiolytic activity when it is orally administered, and the minimum effective dose thereof for single administration is as high as 100 mg/kg. Therefore, the expected effects cannot be fully obtained unless a large amount of the bromacil is administered. With respect to the N.sup.3 -substituted uridine derivatives referenced as (2), although the aforementioned patent publication discloses their hypnotic effects, their anxiolytic activity and particular data regarding the same are not disclosed therein.
An object of the present invention is to provide an anxiolytic drug which comprises as an active ingredient a compound which has a uracil skeleton and low side effects such as those mentioned above.